Fiber-optic light sources are generally well known and are used in a broad range of applications. For example, in the medical field, fiber-optic illuminators such as various light sources, fiber-optics, and endoscopes are widely used in endoscopy. Bulb-based medical fiber sources are currently manufactured by Stryker, Smith-Nephew, Storz, Olympus, and others. Light sources and fiber-optics are commonly used for microscopy illumination, with lamp-based products offered by Zeiss, Welch-Allyn, Dolan-Jenner, and others. Fiber-optic illumination systems are also used with industrial boroscopes and machine vision systems. While the preceding devices primarily provide ‘white’ light for illumination, other fiber-optic light sources providing ‘blue’ light in the wavelength range 420-490 nm are used in photodynamic therapy for pediatric hyperbilirubinemia.
Systems having light sources and fiber-optics for light transmission can also provide one or more defined wavelengths of light for fluorescent excitation in biological and other research fields. For many applications, a round beam spot is desired, for example, an exam light, a spot light and a fiber optic light. In the case of a fiber optic light, the goal is to deliver more light through a fiber bundle. A fiber bundle is comprised of numerous fiber strands tightly packed together. All the fiber strands end at a cylindrical metal ferell. The fiber strands are then bound and polished. Light comes in from one end of the fiber bundle and is emitted out from the other end of the fiber bundle. When the fiber bundle end is round, the effective light transmission area is round. If the incoming light beam is from a rectangular or square shaped light source, depending on the size, only portion of the light is transmitted or portion of the fiber strands are utilized resulting in inefficiency.
For example, the emitting area inside an LED package is the footprint of the die or die cluster, which usually has a square or rectangular shape. When a lens system is used to collect light from LED(s), the output beam is the image of the LED die and is thus square or rectangular. This square or rectangular output beam therefore does not match the round fiber end and causes inefficiency because some light is lost in the transition. For many applications, it is desirable that the output light in a range of wavelength or color different than the source. Some manufacturers use additional filters to achieve that, increasing system complexity and cost. With the inventive light guide, filters can be integrated with the light guide by film deposition or color doping. The output beams currently use devices such as LEDs that are closely tied to the fiber optics. However, the shape of the LEDs still results in some inefficiencies. Another light guide is a thin plate for a surface light source that generates a highly uniform light. Such a light guide still creates inefficiencies as light is lost between the light source and the light guide.